ul, ol { list-style: none; }
table {
  border-collapse: collapse;
  border-spacing: 0;
}
body, h1, h2, h3, h4, h5, h6, hr, p, blockquote, /* structural elements 结构元素 */
dl, dt, dd, ul, ol, li, /* list elements 列表元素 */
pre, /* text formatting elements 文本格式元素 */
fieldset, lengend, button, input, textarea, /* form elements 表单元素 */
th, td { /* table elements 表格元素 */
      margin: 0;
      padding: 0;
}

.fr{
  float:right;
}

.fl{
  float:left;
}

.clearfix:after{
  display: block;
  clear: both;
  content: "";
  visibility: hidden;
  height: 0;
}

.pos-a{
  position:absolute;
}

.pos-r{
  position:relative;
}

.pos-f{
  position:fixed;
}

